One particular way I'm afraid this could affect cryptocurrency is when privacy features come in. For example, if Bitcoin gets MW and QCs will be used against BTC, can't it basically be used to generate all possible seeds and not only link current addresses to each other (since coin control is no privacy enhancer anymore as soon as they have your seed) but also see where the money has come from (or been sent to)?
I actually haven't thought of this at all and I was more fixated on how it would just exploit public key cryptography. I don't think QCs will be able to speed up the generation of seeds (or addresses), that significantly. After all, address generation involves both SHA256 as well as RIPEMD-160 while HMAC-SHA512 is used for BIP32 seeds to master private keys. While they should provide a speedup through Grover's algorithm, I doubt it would be fast enough to exhaust the key space. But of course, the xpub will be vulnerable to quantum computers the same way as how exposed public keys are. 
Topic: How will Quantum computing affect Bitcoin? - page 3. (Read 525 times)
One particular way I'm afraid this could affect cryptocurrency is when privacy features come in. For example, if Bitcoin gets MW and QCs will be used against BTC, can't it basically be used to generate all possible seeds and not only link current addresses to each other (since coin control is no privacy enhancer anymore as soon as they have your seed) but also see where the money has come from (or been sent to)?
My fear is that they are using very advanced technologies before we even hear about them, hence being able to control the network (only in a surveillance, view-only mode!) in a way we previously thought was not very likely.
But as others said, if BTC is under attack through QC then there are so many other corporations, banks, governments etc that would be under a very serious threat as well. I think we can only suppose stuff about the damage QC can do until it becomes a consumer-end product. But by then, all the potentual threats are probably going to be erradicated..
My fear is that they are using very advanced technologies before we even hear about them, hence being able to control the network (only in a surveillance, view-only mode!) in a way we previously thought was not very likely.
But as others said, if BTC is under attack through QC then there are so many other corporations, banks, governments etc that would be under a very serious threat as well. I think we can only suppose stuff about the damage QC can do until it becomes a consumer-end product. But by then, all the potentual threats are probably going to be erradicated..
But from what I've read (since there are plenty of threads here on this topic!) Bitcoin is pretty much safe from quantum computing and the only weakness (albeit theoretical) may be in the address reuse. (If I understood right). However, there are a lot of things in this world protected by cryptography, same or weaker than Bitcoin's, if this is hacked the problems will be .. generalized.
As well as transactions that were in P2PK, which means most of the coins mined in the early days are vulnerable. It is not difficult to solve this issue for the transactions in the future but those with exposed public keys will inevitably be vulnerable still.Important note: Most of the encryptions that you're using nowadays will be broken in tandem. Whether Bitcoin is a suitable target, it's too early to tell.
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Its one of the most popular topics here on the forum, I got bored of copying links so I stopped at around 20.
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Its one of the most popular topics here on the forum, I got bored of copying links so I stopped at around 20.
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Quantum computers are exceptionally costly to build and only a couple of nations have shown interest in it! If you think hackers will use such computers to launch an attack on cryptocurrencies like bitcoin, then you are daydreaming. Quantum computing is not yet a threat to cryptography, at least not now and not in immediate future!
Actually they've started to also build 5000$ quantum computers too. Of course, they are very weak (2 qbit) hence they don't need liquid helium for cooling.
And I think that you are also wrong about government financed quantum computers. In the same way super computers were used for crypto mining by this or that scientist with access to them, I can also expect this kind of "accidents" happen now and then with quantum computers too in the future.
But from what I've read (since there are plenty of threads here on this topic!) Bitcoin is pretty much safe from quantum computing and the only weakness (albeit theoretical) may be in the address reuse. (If I understood right). However, there are a lot of things in this world protected by cryptography, same or weaker than Bitcoin's, if this is hacked the problems will be .. generalized.
It has been explained to me, albeit, in layman's terms, that one of the reasons our modern cryptography works so well on classical computers is that they rely on prime factorization which classical computers don't do so well. This has been key to maintaining our computers and networks secured. One of the things Quantum computers do better than classical computers is prime factorization. How will the advent of Quantum computing impact cryptography? Will technologies like blockchains and bitcoin be affected?
Quantum computers are a reality and not a myth anymore! Companies like IBM, Google have invested billions in their quantum computing project and has seen a preliminary success. It's definitely a threat to cryptography but not an immediate one!
Quantum computers are exceptionally costly to build and only a couple of nations have shown interest in it! If you think hackers will use such computers to launch an attack on cryptocurrencies like bitcoin, then you are daydreaming. Quantum computing is not yet a threat to cryptography, at least not now and not in immediate future!
We don't know the current peak capability of quantum computing as it is still in its early stages but one thing is sure that it will be a problem for bitcoin because as what is on the paper says about quantum computing, it will be far faster than any computer in the market and in any laboratories.
You might be right but I am a firm believer that it can affect bitcoin big time, we can't see the peak but we can still imagine what it will do, remember the first computer which is the size of one room, they were much slower back then but we came to the stage that almost every household has a computer which means that quantum computer capabilities might do what we didn't expect it to do at unexpected speed.We also have to stop telling people that quantum computing will be able to hack the private key of everyone, yes it has faster calculations but that doesn't mean that it will crack the key in a matter of days, if right now the current brute force duration is the heat death of the universe, maybe with quantum computing, the time it takes will be cut in half but that is still a whole lot of millennia.
I find it funny that people are talking about quantum computers breaking the security of blockchain so I wouldn't want them people to stop telling about it because I want them to see what they are going to say when you ask them why. Is that really the time it takes to crack the private key with brute force? That is a really long time, I might do some quick search about the duration but I am sure that it will not be as long as the death of universe. 
We don't know the current peak capability of quantum computing as it is still in its early stages but one thing is sure that it will be a problem for bitcoin because as what is on the paper says about quantum computing, it will be far faster than any computer in the market and in any laboratories. We also have to stop telling people that quantum computing will be able to hack the private key of everyone, yes it has faster calculations but that doesn't mean that it will crack the key in a matter of days, if right now the current brute force duration is the heat death of the universe, maybe with quantum computing, the time it takes will be cut in half but that is still a whole lot of millennia.
It has been explained to me, albeit, in layman's terms, that one of the reasons our modern cryptography works so well on classical computers is that they rely on prime factorization which classical computers don't do so well. This has been key to maintaining our computers and networks secured. One of the things Quantum computers do better than classical computers is prime factorization. How will the advent of Quantum computing impact cryptography? Will technologies like blockchains and bitcoin be affected?
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